Some relevant and useful additions:

*SASS-stylesheets* - for even more pretty styled forms in all browsers (mixins for different form layouts, etc.)
"http://github.com/activestylus/formtastic-sass":http://github.com/activestylus/formtastic-sass

*TextMate-bundle* for Formtastic:
"http://github.com/grimen/formtastic_tmbundle":http://github.com/grimen/formtastic_tmbundle

*In-place editor* for Formtastic:
"http://github.com/rubymood/jintastic":http://github.com/rubymood/jintastic

*ValidationReflection* - for auto detecting :required options in inputs fields by checking the validations on the model (only required with Rails 2)
"http://github.com/redinger/validation_reflection":http://github.com/redinger/validation_reflection

*ClientSideValidations-Formtastic* the Formtastic plugin for "ClientSideValidations":https://github.com/bcardarella/client_side_validations:
"https://github.com/dockyard/client_side_validations-formtastic":https://github.com/dockyard/client_side_validations-formtastic

*Formtastic jRails Autocomplete* - An input plugin for Formtastic to render autocomplete fields automagically using jQuery:
"https://github.com/faulkner/formtastic_jrails_autocomplete":https://github.com/faulkner/formtastic_jrails_autocomplete

*E9s* - i18n additions: "http://github.com/archan937/e9s":http://github.com/archan937/e9s

*Formtastic Without ActiveRecord* – A guide to using Formtastic on forms that don't have an ActiveRecord/ActiveModel model: "http://dondoh.tumblr.com/post/4142258573/formtastic-without-activerecord":http://dondoh.tumblr.com/post/4142258573/formtastic-without-activerecord

*Formtastic With Twitter Bootstrap* - A gem that generates Twitter Bootstrap-friendly HTML using Formtastic.
"https://github.com/mjbellantoni/formtastic-bootstrap":https://github.com/mjbellantoni/formtastic-bootstrap

*Pwdcalc* - A gem to create password field/-strength meter combinations:
"https://github.com/trimentor/pwdcalc":https://github.com/trimentor/pwdcalc

*formtastic_image* - An input plugin for formtastic to render file fields with an image preview for paperclip attachments:
"https://github.com/elandesign/formtastic_image":https://github.com/elandesign/formtastic_image

*canvas to image* - An input plugin to use a canvas for drawings (mostly autographs). the drawing will be submitted to the server
"Link to Gist":https://gist.github.com/4678219